Final Counts of Monoclonal Gammopathy of Renal Biopsies After Radiographic Imaging Analysis

Document Type

Conference Proceeding

Publication Date

3-2025

Publication Title

Laboratory Investigation

Abstract

Background: Monoclonal gammopathy of renal significance (MGRS) is characterized by variants of monoclonal protein-associated nephropathies with less than 10 % of monoclonal plasma cells in bone marrow biopsies (except monoclonal cast nephropathy). A lytic lesion on PET CT or a lesion greater than 5 mm on MRI is another myeloma-defining event in patients with monoclonal protein-associated diseases. This study assessed how likely patients with MGRS can reveal lytic lesions on imaging for finally defining MGRS in them. Design: Among 130 cases with monoclonal protein-associated nephropathies, 38 patients with MGRS were identified, following the exclusion of bone marrow biopsies. The patient’s charts were retrospectively searched for whole-body bone scans, PET CTs, or MRIs. Patients with DEXA scans were not included in the negative imaging counts. The imaging studies were assessed for the presence of lytic lesions in the bone. Results: A total of 19/38 (50 %) patients had no imaging studies performed to assess for bone lesions explicitly. Two out of 19 (11%) cases were identified with lytic bone lesions; one on a bone scan and the other one on a CT scan (Figure 1, lytic lesion with dotted circles and Table 1 for 19 available image cases); thus, they were excluded from MGRS. 17 out of 19 (89 %) patients had negative imaging results for lytic bone lesions, therefore remaining as MGRS. Six patients were deceased at the time of review. Conclusions: Our data indicate that a small percentage (11 %) of MGRS patients can be further excluded from the MGRS category due to the finding of bony lytic lesions. Therefore, the two cases with lytic lesions should be categorized into the heavy burden group. This study highlights the importance of doing a full-body bone scan or pet CT in any patient with MGRS-defining kidney disease, as a bone marrow biopsy alone cannot entirely rule out patchy myeloma. Therefore, we propose performing bone surveys in all cases of MGRS, ideally before performing a bone marrow biopsy, to provide the hematopathologist with the best tissue for a myeloma workup.

Volume

105

Issue

3 Suppl

First Page

63

Comments

114th Annual Meeting of the United States and Canadian Academy of Pathology, March 22-27, 2025, Boston, MA

Last Page

64

DOI

10.1016/j.labinv.2024.103495

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